The present invention generally relates to temperature control systems for maintaining the temperature of an electronic device at a predetermined temperature such as while the device is being tested.
Electronic devices, such as integrated circuits, are often tested at temperatures below ambient temperature. This requires a supply of a coolant below the test temperature, which can be used both to bring the device to the setpoint temperature and to act as the conduit for heat rejection when power is applied to the device. In one such implementation, liquid refrigerant at ambient temperatures is expanded in an isenthalpic process to provide cooling at temperatures below ambient at a thermal head. See, for example, pending application Ser. No. 09/871,526, filed on May 31, 2001, which is hereby incorporated by reference.
The temperatures that can be achieved at the thermal head with this process depend on the refrigerant(s) used as well as the temperature and pressure of the refrigerant at the entrance of the isenthalpic expansion device. Generally, as pressure increases or as temperature decreases for the unexpanded refrigerant, more cooling and/or lower temperatures can be achieved at the thermal head. However, there is a limit to the increase in pressure allowable by the unexpanded refrigerant due to the gas physical properties as well as due to practical structural considerations for supply tubing.